<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    .link {
      background-color: #d2d2d2;
    }

    /* .link:hover {
      background-color: pink;
    } */

    .link:active {
      background-color: #7c2d99;
    }

    .block {
      display: none;
      background-color: green;
    }

    .link:hover .block {
      display: block;
    }
  </style>
</head>

<body>
  <script>
    /*
      1. hover 悬浮
      2. active 点击
      3. link 未访问过的链接
      4. visited 访问过的链接，只能改颜色
    */
  </script>
  <a href="#" class="link">
    慕课网学习的好地方
    <div class="block">我是隐藏快</div>
  </a>
</body>

</html>